双向协同萃取精馏分离乙酸甲酯-甲醇-水工艺研究(硕士)

双向协同萃取精馏分离乙酸甲酯-甲醇-水工艺研究(硕士)(论文32000字)
中 文 摘 要
共沸体系的分离，常规的分离工艺很难得到高纯度的产品，且分离能耗高。如今，环境污染日益严重，资源短缺愈演愈烈，化工行业的节能减排问题再次成为焦点。精馏过程的能耗主要在于分离，人们也一直致力于寻找高效的节能工艺。针对共沸体系的分离，萃取精馏工艺是常用的方法，对常规工艺改进的协同萃取精馏工艺和变压萃取精馏工艺显得更加高效。多效热集成精馏、提浓预分塔、中间换热、机械蒸汽再压缩（MVR）热泵技术逐渐成熟，有机朗肯循环（ORC）低温余热发电技术作为一种新型的余热回收技术开始崭露头角。
本文选用包含乙酸甲酯-甲醇和乙酸甲酯-水两组最低共沸的乙酸甲酯-甲醇-水三元混合体系作为研究对象。汽液平衡实验测得两组体系的气液相组成数据，数据回归拟合修改aspen Plus的二元交互参数。计算体系相对挥发度大小确定最佳萃取剂，以年投资总资产（TAC）为评价指标优化工艺参数，比较常规单溶剂三塔、双溶剂四塔精馏工艺和双溶剂协同萃取精馏工艺，发现双溶剂协同萃取精馏工艺要明显优于其他工艺流程。
乙酸甲酯-甲醇和乙酸甲酯-水属于压力敏感的共沸体系，依据压力、萃取剂对相对挥发度的关系确定各精馏塔的操作压力和最佳萃取剂。模拟比较两塔变压萃取精馏和三塔变压萃取精馏工艺，并在此基础上引入热集成技术和MVR热泵节能技术。就TAC而言，较三塔变压萃取精馏工艺而言，两塔变压萃取精馏工艺显得更具优势。
通过aspen Plus正交模拟实验得到最佳萃取比，在双溶剂协同萃取精馏工艺的基础上引入节能技术。针对乙酸甲酯回收塔和甲醇回收塔，引入带中间换热器的MVR热泵精馏工艺；将溶剂回收塔分为粗分塔和精制塔，溶剂粗分塔耦合MVR热泵技术，溶剂精制塔耦合ORC技术。ORC低温余热发电技术，通过优化工质、蒸压压力和冷凝压力，确定最大发电量并供给压缩机。
实验结果表明：水和乙二醇是分离该体系较为合适的萃取剂，常规双溶剂协同萃取精馏工艺与常规双溶剂四塔萃取精馏工艺和常规单溶剂三塔萃取精馏工艺相比，其能耗分别减少约45.6%和12.4%，TAC分别降低约43.5%和11.6%；
双溶剂协同萃取精馏基础上的节能措施节能效果明显，就TAC而言，乙酸甲酯回收塔降低约31.34%，甲醇回收塔降低约50.45%，溶剂回收塔降低约23.29%。
两塔变压萃取精馏较三塔变压萃取精馏工艺更优，其能耗可以减少约44.83%，TAC降低约47.74%。两塔变压萃取精馏基础上的MVR热泵技术比热集成技术更优，其能耗可以减少约76.00%、77.96%，TAC降低约45%、51.43%；
因此，对于类似的共沸体系的分离可以采用上述精馏技术以最大程度上降低分离能耗。

关键词:乙酸甲酯-甲醇-水；协同萃取；变压萃取；热集成；ORC耦合MVR热泵；中间换热

ABSTRACT
The conventional separation of azeotropic system is relatively more difficulty and with high energy consumption. Nowadays, the increasingly serious environmental contamination and intensified resource shortages make the energy saving and emission reduction issues become the focus in chemical industry once more. Distillation energy consumption mainly lies in separation, which forces the exploration of efficient rectification energy saving method imperatively. Extractive distillation is a common method for the separation of azeotropic system. The enhancement extraction and pressure swing distillation process presented to be more efficient. Multi-effect distillation, pre-concentration, inter-reboiler, mechanical vapor recompression (MVR) heat pump technology tends to be mature, the Organic Rankine Cycle (ORC) technology is emerging as one of the freshest technology.
In this paper, methyl acetate-methanol-water ternary mixture was selected as the research object, in which exists two lowest azeotropic points including methyl acetate-methanol and methyl acetate - water systems. The vapor-liquid equilibrium constant was measured by experiment and the binary interaction parameters were modified by aspen Plus. The solvents of system were determined according to relative volatility. Total annual cost (TAC) serves as the evaluation index to optimize the process parameters. Comparing the single solvent three column extractive distillation with double solvent four column extractive distillation process, the later is superior to other techniques.
Methyl acetate-methanol and methyl acetate-water azeotropic system belong to pressure sensitive system. The operating pressure is determined according to the relationship between the pressure and the relative volatility, and the appropriate solvents were selected on the basis of the relative volatility of the system. Comparing two column pressure-swing distillation with triple column pressure-swing distillation, and on the basis of which heat integrated and MVR heat pump technology were introduced. DCPSED process appears to be more advantages than TCPSED.
The optimum solvent ratio was obtained by the orthogonal experiment. Energy-saving technology was introduced on the basis of the synergistic extractive distillation process including the introduction of MVR heat pump with inter-reboiler distillation process for methyl acetate and methanol recovery column; the solvent recovery column contains pre-concentration column and refining-concentration column. MVR heat pump technology was directly added into pre-concentration column. ORC waste heat power generation technology was used to refining-concentration column due to the high temperature of high bottom production. The maximum power generation was supplied to compressor through the optimum of steam pressure and condensing pressure.
The results show that water and ethylene glycol are the more suitable solvent for the separation system. Comparing double solvent synergistic extraction distillation process, double solvent four column extractive distillation and single solvent three column extraction distillation process, we found that double solvent four column extractive distillation process was the optimum process. The energy consumption were reduced by 45.6% and 12.4% respectively, the TAC decreased by about 43.5% and 11.6% in terms of double solvent synergistic extraction distillation process to double solvent four column extractive distillation and single solvent three column extraction distillation process;
The energy-saving projects based on double solvent synergistic extraction distillation process were obvious. TAC was reduced by 31.34%, 50.45% and 23.29% for methyl acetate, methanol and solvent recovery column, respectively.
DCPSED is superior to TCPSED process and the energy consumption can be reduced by 44.83%, TAC decreased by 47.74%. DCPSED with MVR heat pump technology is better than integrated technology and its energy consumption can be reduced by 76%, 77.96%, TAC decreased by 45%, 51.43%;
Therefore, the above separation technologies can be used to reduce energy consumption to the great extent.

KEY WORDS:methyl acetate-methanol-water;synergistic extraction; pressure-swing extraction; heat integrated; ORC coupled with MVR heat pump; inter-reboiler

目  录
1绪  论    9
1.1 引言    9
1.2特殊精馏节能技术概述    10
1.2.1萃取精馏    10
1.2.2变压萃取精馏    11
1.2.3共沸精馏    13
1.3精馏节能技术    13
1.3.1塔系间热集成精馏    14
1.3.2多效精馏    14
1.3.3中间换热    15
1.3.4内部热集成精馏    15
1.3.5 MVR热泵技术    16
1.3.6 ORC技术    18
1.4 aspen Plus软件简介    19
1.5研究路线及费用模型    20
1.5.1经济效益评价    20
1.5.2热力学分析    21
1.6课题研究内容及目标    22
2. 萃取剂筛选    23
2.1研究体系    23
2.2萃取剂筛选原理    23
2.3萃取剂筛选模拟    24
2.4萃取剂筛选实验    25
2.5小结    27
3低浓度乙酸甲酯-甲醇-水分离体系萃取精馏    28
3.1常规流程简述    29
3.2双溶剂协同萃取精馏工艺    32
3.3有效能分析    34
3.4小结    35
4.高浓度乙酸甲-甲醇-水精馏工艺    36
4.1单溶剂三塔萃取精馏    36
4.2双溶剂协同萃取精馏    36
参 考 文 献    60